Mercruiser 190 Exhaust Elbow (Overheating)

Famous 190, high speed overheating change raw water pump, check flow, when i pull the pipe off the exhaust elbow there is aton of water coming from the heat exchanger, but there is also water spraying out with exhaust from the water port on the side of the exhaust elbow.... is this normal?

if i take off the exhaust elbow and put a garden hose on the inlet port the water does not flow freely it actually builds pressure in the exhaust elbow and will spray back out if i remove the hose, i'd say maybe 30% of the water flows through the exhaust elbow the rest just packs in there...

Re: Mercruiser 190 Exhaust Elbow (Overheating)

There have been a couple of questions about restricted exhaust lately, so I went out and took a look at mine. It looks like that is just a fitting that should dump the water into the exhaust with no restriction at all. I wonder if maybe your exhaust shutter has failed and is blocking the exhaust passage, causing backpressure that might reduce the flow. You could try removing the rubber bellows and checking to see if the shutters are intact http://www.mercruiserparts.com/Show.../46.png&inbr=908&bnbr=230&bdesc=EXHAUST+ELBOW. With the bellows off check the water flow through the port, if it flows freely, then the obstruction must be downstream. Good luck.

Re: Mercruiser 190 Exhaust Elbow (Overheating)

I also tried with the exhaust elbow disconnected, so wondering if it's normal and under speed a vacuum is created?




http://www.mercruiserparts.com/Show_pictures3.asp?dnbr=%2012488&ivar=IMAGES/CRUISER/12488/21.png&inbr=908&bnbr=100&bdesc=EXHAUST+MANIFOLD+AND+EXHAUST+ELBOW+%28ALUMINUM%29

17 98562A6 EXHAUST ELBOW AND RESERVIOR ASSEMBLY

even when off the boat if i put a hose on #24 and apply full hose pressure 30% of the water comes out, when i remove the hose water sprays back out of #24 like it was pressurized

Re: Mercruiser 190 Exhaust Elbow (Overheating)

Seems like it should flow through there with no resistance. Maybe you could try to remove #24 and see if there is some blockage in there. I guess as a last resort you could pull the reservoir off and turn it upsidedown and take a a look. I am not sure what it looks like, maybe a narrow slot or opening that is clogged with something.

Re: Mercruiser 190 Exhaust Elbow (Overheating)

OK finally found a photo that I was looking foe. The third one here:http://cgi.ebay.com/ebaymotors/MERCRUISER-470-EXHAUST-ELBOW-CLOSED-COOLING-4-7-LITRE-/110680593350 shows the inside of the exhaust manifold, and it looks like the water goes in the fitting (on the photo left side) and around the manifold and out the slot at the top of the photo. I'll bet you have a clog in there. Best way to unclog would probably be to remove the reservoir to work on it. Thanks for helping me lean something today LOL.

Re: Mercruiser 190 Exhaust Elbow (Overheating)

Just found a reference that water should flow freely through the elbow

Re: Mercruiser 190 Exhaust Elbow (Overheating)

Thought so LOL, let us know how you make out.

Re: Mercruiser 190 Exhaust Elbow (Overheating)

flushed cooling system, flushed raw water system, changed raw water pump, removed old flapper parts from lower foot....

timing double checked 1500 rpms temps stay at 160, 3000 climbs to 200 1500 rpm comes back down to 160.

Removed exhaust elbow cleaned it out hose runs freely through it will test tomorrow fingers crossed :s

I did notice that my coolant lines were not pressurized on the engine though

Re: Mercruiser 190 Exhaust Elbow (Overheating)

Ok took her out today 2000rpm and under it's fine, 3000rpm planing infrared on the temp sensor said 204, come down to 1500rpm temp goes down to 170, also the heat exchanger was at 190, so not enough water is going through

things done:
new water pump
flushed raw system
flushed closed system
flushed heat exchanger
check ps cooler
removed old flapper from foot
flushed exhaust manifold

things to look at:
supply hose from foot to bell housing
still more blockage in the exhaust passages?

was thinking of t'ing off the output from the heat exchanger to see if there is lots of flow, then that would mean some exhaust blockage

if the exchanger is 194 and coolant 204 there isn't enough water

Re: Mercruiser 190 Exhaust Elbow (Overheating)

Solved, kinked tube on the bellhousing